420 



FUNAFUTI ATOLL. 



Island. These measure 5 mm. in length, and have an additional 

 spiral cord. 



Though certainly distinct, R. transenna, Watson, has much 

 resemblance to this species. R. clathrata, Adams, appears to 

 differ slightly by coarser sculpture. 



RlSSOINA GEMMEA, Sp. nOV. 

 (Fig. 11). 



Shell narrow, conical, white. Whorls eight (including two em- 

 bryonic), rounded, suture lightly impressed. Embryonic whorls 

 smooth, shining, apparently two, but a study of several species of 

 the genus suggests that the topmost apparent 

 whorl may contain several whorls wound in the 

 same plane and concealed within the outermost. 

 Sculpture the last whorl is evenly and closely 

 latticed by the intersection of eleven slender 

 spiral cords, and about forty-two delicate longi- 

 tudinal ribs ; a smooth shining bead marks each 

 crossing of the sculpture. The longitudinal ribs 

 are slightly stronger than the spiral cords, a 

 quarter of the breadth of their interstices, 

 slightly oblique and curved; they cross regularly 

 from base to suture and continue without stop- 

 page at the suture, from whorl to whorl of the 

 spire. Ascending the upper whorls, the spiral 

 cords become fewer and gradually vanish leaving 

 as vestiges a few denticles on the ribs. The spaces 

 enclosed by the major sculpture are square shallow 

 pits, spirally striated. Round the base are wound 

 throe or four irregularly beaded cords. 

 Aperture oblique, produced in front, contracted anteriorly to a 

 short spout ; columella sharply recurved at the base, extending 

 across the body-whorl as a thick layer of callus ; posteriorly the 

 lip is sharply folded at its junction with the body whorl. The 

 outer lip is much thickened, grooved upon the inner face, denticu- 

 late on the profile and with a heavy callus behind. Length 4, 

 breadth 1| mm. 



One specimen in shallow water in the lagoon. 

 In this species the grains seem to be smaller and more numerous 

 than in any other beaded Rissoina described. 



RlSSOINA POLYTROPA, Sp. nOV. 



(Fig. 12). 



Shell ovate, fusiform, narrow, white. Suture impressed. Whorls 

 seven, including two embryonic. The last whorl descends from 

 the spiral plane of its predecessors until reaching the aperture, 

 when it ascends suddenly and rapidly, the varix mounting up the 

 preceding whorl for three tiers of spiral lyrse. The shell is thus 



Fig. n. 



